Gas-stream heating method



"Nov. 17, 1970 J; H. FLYNN GAS-STREAM HEATING mmnon Filed 001:. 1, 1969John INVENTOR HEW/717 fiozwg/r United States Patent 3,541,190 GAS-STREAMHEATING METHOD John H. Flynn, 234 Elk Ave., New Rochelle, N.Y. 10804Continuation-impart of application Ser. No. 759,741, Sept. 13, 1968,which is a continuation-in-part of application Ser. No. 559,246, June21, 1966. This application Oct. 1, 1969, Ser. No. 868,960

Int. Cl. F231 7/00 US. Cl. 263-52 Claims ABSTRACT OF THE DISCLOSURE Aburner installation located in a gaseous stream to be heated has aburner casing with a flame surface to which lead main and pilot flameports for flames projecting downstream of the gaseous stream into aflame space therein. The installation further provides for operation ofthe burner, including shielding of the flames from extinction by partialvacuum induced by the passing stream, by constantly delivering to apilot space part of the flame space a gaseous medium at a rate tosuppress therein any stream-induced flame-extinguishing partial vacuumat any stream velocity.

This application is a continuation-in-part of my prior application Ser.No. 759,741, filed Sept. 13, 1968, now abandoned which was acontinuation-in-part of my prior application Ser. No.v559,246, filedJune 21, 1966, now Pat. No. 3,437,322.

This invention relates to a gas-stream heating method, and moreparticularly to a gas-stream heating method involving flame as theheating medium.

The type of gas burner used in the method with which the presentinvention is concerned is a gas-fed flame burner installed within adirected utility stream of air or other gas for heating the same, withthe burner flame being directed down-stream of the passing stream. Suchburners are used as heaters for all kinds of space heating especially,though not exclusively, in industrial establishments, and they are alsoused for other purposes such as heating large volumes of air ornon-combustible gases in industrial processes, for example. It is amongthe more important requirements of these heaters that for a burner inany installation the heat of the burner flame must be able to flash thetemperature of the passing air or gas to a high peak at maximumoperational stream velocity. This requires, in turn, that the burnerflame must maintain in the air or gas stream a zone of very high heatintensity. Another important requirement of these heaters is flexibilityin operation over a wide range, to the end of heating passing air or gasto the same or different temperature peaks.

Among known flame burners that would best meet the aforementionedrequirements of these heaters are those of high-capacity flameperformance which are supplied with a quantitatively regulatablecombustible mixture of preferably fixed air-gas ratio for sustaining theflames without any outside or secondary air and, hence, produce flamesof high heat-output at widely regulatable flame velocity or driveindependent of the velocity of the passing air or gas stream. However,in these high-capacity burners the main or operating flames aresustained by pilot flames without which the main flames would extinguishsince the rate at which the combustible mixture is fed to the latter isusually greater than the rate of flame propagation, and it is for thisreason that these burners are of no avail as air heaters since the airor gas passing the burners at most operational stream velocities createsat the flame side of the burners a notable vacuum in which no pilotflames can persist. Recourse has, therefore, been had to burners ofmodified construction and operation in which at the 3,541,190 PatentedNov. 17, 1970 more prevalent higher operational flame settings, theusual pilot flames are lacking, with the flame ports being then suppliedwith more or less pure gas and the combustion air therefor being largelysecondary air diverted from the air stream to-be-heated into combustingadmixture with the gas beyond the flame ports for maintenance ofoperating, flames. However, while these modified burners are generallysatisfactory, they are lacking in a few, but important, respects. Thus,the drive of the flames is dependent upon, and hence limited by, thevelocity of the diverted combustion air from the passing stream, so thatthe flames lack any appreciable drive are are massed in rather closeproximity to the burners which thereby are unduly subjected to heat.Also, correct regulation of the gas admitted to these burners forcomplete combustion on admixture with the diverted combustion air fromthe passing stream at varying operating velocity of the latter involvesrather intricate gas flow control. Further, these burners do not lendthemselves to many applications involving eificient heating of gasstreams that lack air or oxygen and, hence, are incapable of furnishingthe combustion air for the burners without which the latter cannotperform.

It is the primary aim and object of the present invention to provide forsuccessful operation of an air or gas heating flame burner so that thesame has the aforementioned high-capacity flame performance in an air orany other gaseous stream, including a stream devoid of oxygen.

It is another object of the present invention to devise a method ofsuccessfully operating a high-capacity flame burner in an air or anyother gaseous stream, which features effectively shielding from thevacuum effects of the passing air or gas stream those critical flameareas of the burner adjacent the flame ports where such vacuum effectswould otherwise extinguish the pilot flames and even the main flames ifthe pilot flames were not extinguished, so that any velocity of thepassing stream the pilot flames will remain undisturbed and sustain themain flames at any heat-output and drive as fully as though thesurrounding air or gas were not moving. In thus achieving high-capacityflame performance of a burner in an air or gas stream, the flame will,on regulation for high heatoutput and drive, strike deep into thepassing stream of any velocity and there maintain an extensive andhighly heated zone which does not unduly heat the burner but in whichthe streaming air or gas will at even maximum velocity have somedefinite dwell and be in most intimate heat-exchange relation not onlywith the flame itself but also with its products of combustion.

Another object of the present invention is to achieve, in theaforementioned method of operating a high-capacity flame burner in anair or other gaseous stream, eflective shielding of the critical flameareas from the vacuum effects of the passing air or gas stream, byconstantly delivering to a pilot space part of the flame space in thestream, within which the bases of the main flames are in ignitingrelation with the pilot flames, a gaseous medium at a rate to suppressin this pilot space part any stream induced flame-extinguishing partialvacuum at any stream velocity.

A further object of the present invention is to provide in theaforementioned method for supplying the pilot space part of the flamespace in the stream with air or another gaseous medium preferably andadvantageously by simply diverting the same from the stream into thepilot space part.

Further objects and advantages will appear to those skilled in the artfrom the following, considered in conjunction with the accompanyingdrawings.

In the accompanying drawings, in which certain modes 3 of carrying outthe present invention are shown for illustrative purposes:

FIG. 1 is a side view of a flame burner operated in accordance with amethod embodying the present invention;

FIG. 2 is a section through the burner as taken on the line 22 of FIG.1;

FIG. 3 is a cross-section through a modified burner, and

FIG. 4 is a part end-elevational and part sectional view of anothermodified burner.

.Referring to the drawings, and more particularly to FIGS. 1 and 2thereof, the reference numeral designates a flame burner for heating astream of air or other non-combustible gaseous matter, hereinafterreferred to as gaseous stream. The burner 10 is to this end suitablymounted, in this instance, within a duct 12 in which a gaseous streamflows in the direction of the arrows 14 past the burner in order to beheated by the burner flames F.

The burner 10 has a longitudinal burner casing 16 with an internalchamber 18 and main and pilot burner slots 20 and 22 which extendsubstantially over the length of the casing 16. The burner slots 20 and22, which are provided in a flame surface 24 of the casing 16, are incommunication with the chamber 18, with spaced restricted ducts 26 inthe casing providing in this instance for communication between thechamber 18 and the pilot burner slots 22 (FIG. 2). Arranged in theburner slots 20 and 22 are burner ribbon assemblies 28 and 30 whichdefine main and pilot flame ports 32 and 34, respectively. The casingchamber 18 is through a conduit 36 supplied with a combustible air-gasmixture which on ignition at the flame ports 32 and 34 sustains main oroperating flames F and pilot flames p, respectively. The chamber 18,which is part-cylindrical about the burner axis x, is in this instanceformed by a through-passage in the casing 16 which is closed at bothends by covers 38 that are mounted at 40 on end flanges 42 of thecasing. The burner casing 16 is in this instance symmetrical about aplane P in which the burner axis x lies and which intersects the flamesurface 24 midway of its width (FIG. 2).

The burner described so far may be entirely conventional, and the samemay be operated for high-capacity flame performance at which the air-gasmixture supplied to the chamber 18 will sustain the main and pilotflames F and 1 without any outside or secondary combustion air.Customarily, air and gas are premixed at a given ratio in a usualpremixer ,(not shown) and the mixture conducted to the chamber 18 atwidely variable volumetric flow rates for sustaining burner flames ofcorrespondingly variable velocities or drive. The air-gas ratio of themixture is usually chosen for optimum heat-intensity of the flames, andthe main flames F are at their maximum setting of particularly highvelocity or drive and also forward projection, but they would extinguishwithout pilot flames p since the rate at which the combustible mixtureis fed to the main flames is in normal burner operation greater than therate of flame propagation. However, if the burner described so far weresubjected in the duct 12 to a gaseous stream at even one of the loweroperational velocities of the latter in most any space-heating or otherinstallation, the vacuum created in the vicinity of the flame surface 24of the burner by the passing air would extinguish the pilot flames pand, hence, also the main flames F, and if such vacuum would perchancenot extinguish the pilot flames p it may well extinguish the main flamesF by interrupting them at their base b. Accordingly, the burnerdescribed so far is of no avail for high-capacity flame performance in agaseous stream of mostany operational velocity.

In accordance with one aspect of the invention, the present burner is bystructurally simple and quite inexpensive conversion adapted forhigh-capacity flame performance in an air stream of most any, and eventhe highest, operational velocities. To this end, provision is made toshield the critical flame areas of the burner, i.e., the pilot flames pand bases b of the main flames F, from the inevitable vacuum produced bythe passing gaseous stream. This is accomplished in a broader sense byproviding the burner with a channel formation outwardly from the flamesurface of the burner casing of which the sides of the channel flank thecritical flame areas of the burner, and continuously delivering to thischannel at the level of the flame surface secondary air ornon-combustible gas at a volumetric flow rate at which it will preventany flame-extinguishing vacuum formation at the critical flame areas bythe passing gaseous stream to-be-heated without, however, having anyadverse effect on the stability of the main and pilot flames at anysetting thereof. More particularly, this channel formation is part of asecondary chamber 50 which is preferably defined by a separate hood 52over the burner casing 16. The hood 52 has opposite end walls 54 and aperipheral wall 56. In the preferred form of the hood 52, its peripheralwall 56 has a part-cylindrical portion 58 and tangentionally continuingplanar portions 60, of which the part-cylindrical wall portion 58 restsagainst, and is at 62 secured to, the end flanges 42 of the burnercasing 16, while the planar wall portions 60 converge toward, and definewith the end walls 54, an opening 64 in the secondary chamber 50 whichis in line with the flame ports 32, 34 and outwardly spaced from theflame surface 24 of the burner casing. The end walls 54 of the hood 52partly close the secondary chamber 50 at its opposite ends between theend flanges 42 of the burner casing 16 and the opening 64, while the endflanges 42 themselves close the remainder of the secondary chamber 50 atits ends (FIG. 2). The end walls 54 of the hood 52 are in this instanceparts of plates 66 which are separate from the peripheral hood wall 56and conveniently clamped between the end flanges 42 of the burner casingand the covers 38 thereon, and the separate end walls 54 are in thisinstance further secured at 68 to outward flanges 70 at the oppositeends of the peripheral hood wall 56.

The part of the secondary chamber 50 between the flame surface 24 andopening 64 is in the form of a channel 72 which is open to the remainingpart 74 of the chamber 50 at both sides 76 and 78 of the flame surface24 (FIG. 2). The depth of this channel part 72 of the secondary chamber50 is in any event adequate to shield the critical flame areas of theburner directly from the passing gaseous stream to-be-heated, and thischannel depth is preferably only several times the maximum height of thepilot flames p as roughly shown (FIG. 2), so that virtually the entiremain flames beyond their base b project at most operational settingsbeyond the opening 64 of the secondary chamber 50 and directly into thepassing gaseous stream to-be-heated.

The secondary air or non-combustible gas, which is to be flown throughthe channel part 72 of the secondary chamber 50 for preventing therein aflame-extinguishing vacuum formation by the passing gaseous streamto-beheated, is preferably and advantageously derived from the passinggaseous stream itself. To this end, the hood 52 is provided, preferablyat the burner side opposite the flame surface 24, with a restricted slot80 which extends over the longitudinal extent of the secondary chamber50 and through which gas from the passing stream is admitted into thelatter. The secondary chamber 50 serves as an expansion chamber in whichthe admitted gas undergoes considearble reduction in pressure andvelocity, and whatever turbulence the gas may develop immediately on itsadmission into this expansion chamber will largely be quelled as itapproaches the channel part 72 of this chamber. This makes for fairlysmooth and moderate-velocity flow of the admitted gas into and throughthe channel part 72 of this chamber and out through the opening 64 intothe passing gaseous stream, at which it will prevent at the,

critical flame areas of the burner any flame-extinguishing vacuumformation by the passing gaseous stream to-beheated without, however,adversely affecting the stability of the flames. In fact, in thepreferred formation of the channel part 72 of this chamber by theconverging planar wall portions 60 of the hood (FIG. 2), the flow of theadmitted gas through this channel part is so smooth that it has beenfound advantageous to pass this flowing gas into even closer proximityto the pilot flames p and the base b of the main flames This is achievedin this instance by providing the converging wall portions 60 of thehood withbafiles 82 which extend over the length of the channel part 72and divert the passing gas generally over the flame surface 24. The gasis thus flown toward the critical flame areas of the burner, and this ispreferred in this specific or any other formation of the channel part72, since the pilot flames then operate with particular assurance in avirtual non-vacuum zone under all conditions and, hence, support andkeep ignited the main flames from minimum to maximum heat output. Thebaflles 82in this preferred channel construction are suitably secured byexemplary screws 84 to the converging hood walls 60. Also secured bysome of the same screws 84 to the peripheral hood wall 56 are spacerbrackets 86 of exemplary V- shape which rest against the burner casing16 and afford the hood additional supoprt on the latter. Admission ofthe gas into the secondary chamber 50 through the slot 80 also makes formaximum cooling of the burner casing 16 and exit end 64 of the chamberby this gas.

The hood 52, and in this instance its peripheral wall 56, is preferablyand advantageously formed in two identical complemental sections '88 and90 which are provided with longitudinal flanges 92 that are kept spacedto define the described slot 80 for admission of the gas, with theseflanges 92 having to this end interposed spacers 94 that are held inplace by bolts 96 which additionally lock the mounted sections 88 and 90to each other. Preferably, the peripheral hood wall 56 is with itsconverging planar wall parts 60 so disposed that the secondary chamber50 is in cross-section also symmetrical about the plane of symmetry P ofthe burner casing 16 (FIG. 2), whereby the flow of gas to the channelpart 72 is evenly divided on the opposite sides 76 and 78 of the flamesurface 24. Further, the hood 52 is in cross-section of teardrop-likeshape (FIG. 2) which offers comparatively little resistance to thepassing gaseous stream to-be-heated, with the flowing gas being shortlyafter passing the hood opening 64 largely reformed into a smooth-flowingstream which does not adversely affect the stability of the main flamesF at any, including their maximum, drive and, hence, projection from thehood opening 64, and is in intimate heat-exchange relation with the mainflames as well as with their products of combustion over thehigh-intensity heat zone of formidable extent maintained by theseflames.

Underlying the described structural conversion of the burner is a methodof its operation which constitutes an important aspect of the presentinvention. The method involved here is that of operating in a gaseousstream a flame burner with main and pilot flames projecting downstreamof the stream into a flame space therein, by feeding the main and pilotflames with a combustible air-gas mixture that requires no secondaryair, at rates greater and smaller than their respective propagationrates, so that the pilot flames will sustain the main flames in a pilotspace part of the flame space within which the bases of the main flamesare in igniting relation with the pilot flames, and shielding the flamesfrom extinction by partial vacuum induced by the passing gaseous stream,by constantly delivering to the pilot space part air or any other gas ata rate to suppress therein any stream-induced flame-extinguishingpartial vacuum at any velocity of the gaseous stream. This method isclearly demonstrated in FIG. 2 in which the pilot and main flames p andF project downstream of the gaseous stream into a flame space thereinwhich extends from the flame surface 24 and encompasses the pilot andmain flames. The pilot flames will sustain the main flames over a pilotspace part of the flame space within which the bases b of the mainflames F are in igniting relation with the pilot flames p, with thispilot space part of the flame space being, in the stream direction, ofthe depth of the described channel 72. Further, the described air or anyother gas is constantly delivered to the pilot space part of the flamespace at a rate to suppress therein any stream-inducedflame-extinguished partial vacuum at any velocity of the gaseous stream.An additional feature of the method lies therein that the air or anyother gas delivered to the pilot space part of the flame space isdiverted from the gaseous stream.

In a more specific sense, the method features shielding of the pilotspace part of the flame space from thereover passing gaseous stream, anddelivering the air or any other gas to this shielded pilot space part ofthe flame space, with this pilot space part being in the exemplaryburner of FIG. 2 the flame area in the described channel 72. Further,the air or other gas is diverted from the gaseous stream in downstreamdirection to the shielded pilot space part of the flame space and isexpanded in the latter. This is demonstrated in the exemplary burner inFIG. 2 where air or any other gas is at diverted from the gaseous streamin downstream direction and is expanded in the secondary chamber 50including the channel thereof.

Reference is now had to FIG. 3 which shows a modified gas-stream heatingflame burner 10a that differs from the described burner 10 of FIGS. 1and 2 primarily by having a secondary chamber 5001 which is of smallersize and volume and also surrounds only part of the burner casing 16a.In this modified burner, the hood 52a may in most respects beconstructed like the described hood 52, except that the part-cylindricalportion 58a of the peripheral hood wall 56a extends between the endflanges 42a of the burner casing 16a and bears against the side of thecasing opposite the flame surface 24a thereof to divide the part 74'a ofthe secondary chamber 50a into non-communicating sections 100 and 102which are, however, in communication with the channel part 72a of thesecondary chamber at opposite sides of the flame surface 24a of theburner casing. The part-cylindrical portion 58a of the peripheral hoodwall 56a has at its opposite ends leg formations 104 by which it ismounted on the end flanges 42a of the burner casing. Air or gas from thepassing stream to-be-heated is admitted into the chamber sections 100and 102 through longitudinal openings 106 which are formed in theperipheral hood wall 56a preferably by striking therefrom baflles 108which direct gas from the passing stream into the openings 106 and,hence, into the secondary chamber 50a. Of course, the modified burner10a is also operated according to the hereinbefore described method.

Reference is finally had to FIG. 4 which shows another modifiedgas-stream heating flame burner 10b that differs from the describedburners 10 and 10a of FIGS. 2 and 3 in that the hood 52b does not extendcompletely around the burner casing 161;. Thus, in the present modifiedburner 10b, the complemental sections 88b and 90b of the hood 52bterminate at 110 and 112 and are there spaced from the adjacent burnercasing 16b to form restricted openings 114 and 116 which are open to thedownstreaming air or gas to-be-heated and admit a metered amount thereofinto the secondary chamber 50b. Of course, this modified burner 10b isalso operated according to the hereinbefore described method.

What is claimed is:

1. In a gas-stream heating method involving a flame burner with main andpilot flame ports for main and pilot flames projecting therefrom in onedirection, the steps of flowing to and beyond said burner in said onedirection any non-combustible gaseous stream including one devoid ofoxygen, with the stream enveloping the burner on passing the same,supplying the main and pilot flame ports with a combustile air-gasmixture at rates greater and smaller than the propagation rates of therespective main and pilot flames thereat, with the air in the mixturebeing adequate for complete combustion of the mixture, and shielding theflames from extinction by the passing stream by constantly delivering tothe pilot flames and nearby bases of the main flames a gaseous medium ata rate to suppress thereat any stream-induced flame-extinguishingpartial vacuum at any stream velocity.

2. The steps in a gas-stream heating method as in claim 1, in which thegaseous medium delivered to the pilot flames and nearby bases of themain flames is diverted from the stream.

3. In a gas-stream heating method involving a flame burner with main andpilot flame ports for main and pilot flames projecting therefrom in onedirection, the steps of flowing to and beyond said burner in said onedirection any non-combustile gaseous stream including one devoid ofoxygen, with the stream enveloping the burner on passing the same,supplying the main and pilot flame ports with a combustile air-gasmixture at rates greater and smaller than the propagation rates of therespective main and pilot flames thereat, with the air in the mixturebeing adequate for complete combustion of the mixture, shielding fromthe passing stream a pilot space which extends from said flame ports insaid one direction and within which the pilot flames are in ignitingerlation with the bases of the main flames, and continuously deliveringto the shielded pilot space a gaseous medium at a rate to suppresstherein any stream-induced flame-extinguishing partial vacuum at anystream velocity.

4. The steps in a gas-stream heating method as in claim 3, in which thegaseous medium is diverted from the stream to the shielded pilot space.

5. The steps in a gas-stream heating method as in claim 3, in which thegaseous medium is diverted from the stream in downstream direction tothe shielded pilot space and is expanded in the latter.

References Cited UNITED STATES PATENTS 3,051,464 8/1962 Yeo et a1. 263193,178,161 4/1965 Yeo et a1. 26319 EDWARD G. FAVORS, Primary Examiner US.Cl. X.R. 26319

